FDA Approves Tysabri® (formerly Antegren)
For The Treatment
of Multiple Sclerosis
November 24, 2004
The United States Food and Drug Administration (FDA) has approved Tysabri® (natalizumab), formerly known as Antegren®, for the treatment of relapsing-remitting forms of multiple sclerosis (RRMS). This approval officially was announced on November 23, 2004 and represents the sixth drug now approved for long-term treatment of MS. The other five are Betaseron® (interferon beta-1b), Avonex® (interferon beta-1a), Rebif® (interferon beta-1a), Copaxone® (glatiramer acetate), and Novantrone® (mitoxantrone).
Marketed by Biogen Idec and Elan Corporation, Tysabri is the first humanized monoclonal antibody to be approved for the treatment of MS. It works by inhibiting adhesion molecules on the surface of immune cells, and is thought to prevent damaging immune cells from crossing the blood-brain barrier from the bloodstream and entering the brain and spinal cord. Tysabri is administered by monthly intravenous infusions every four weeks and must be done by a medical professional.
The FDA granted accelerated approval for Tysabri based on one-year data from its two ongoing two-year phase III trials. Previously, drugs for MS were approved only after two years of phase III trials were complete. The one-year data for Tysabri showed a 66 percent reduction in relapses compared to those on placebo (in the AFFIRM monotherapy trial) and a 54 percent relative reduction in relapses for those taking Tysabri in combination with Avonex, as compared with those taking Avonex alone (in the SENTINEL add-on trial). The FDA requested that the name be changed from Antegren because another drug on the market has a similar name.
Biogen Idec and Elan report that antibodies were detected in approximately 10 percent of participants taking Tysabri at least once during treatment; six percent of participants developed antibodies that remained persistently positive. Persistently positive antibodies were associated with a substantial decrease in efficacy and an increase in certain infusion-related adverse events. Common side effects included headache, fatigue, urinary tract infection, depression, lower respiratory tract infection, joint pain, and abdominal discomfort. The most frequently reported serious adverse reaction was infection (2.1 percent in the treatment group versus 1.3 percent in the placebo group), and included pneumonia. Tysabri had a less than one percent risk of serious allergic reactions in this study.
According to MSAA Vice President and Chief Medical Officer Jack Burks, MD, The FDA approval of Tysabri (formerly Antegren) creates excitement and caution. Excitement stems from the availability of a new class of therapy for MS. Tysabri, a monoclonal antibody, reduced the relapse rate by 66% over placebo and 54% over Avonex in a separate trial when Tysabri was added to Avonex treatment. The MRI data also favors Tysabri.
Dr. Burks notes that caution is advised because:
- Tysabri is not a cure. Some patients still had attacks and ongoing MRI damage while being treated with Tysabri
- The ongoing study only has one year data on effectiveness
- Data on the effects that Tysabri may have on disability progression will not be available until 2005
- While Tysabri appears stronger than Avonex, it has not been compared to other currently available MS treatments (Betaseron, Copaxone, Rebif or Novantrone)
- Longer-term safety data is important
- The cost has yet to be announced
Dr. Burks goes on to say, In summary, we welcome this new unique MS therapy with excellent one year data on relapses, MRI, and safety. Where it fits' with other MS treatments is not known. The other therapies also have FDA approval plus more than 10 years of safety and efficacy data. Additionally, four of the five drugs are self administered. Will Tysabri be a stand alone' treatment or will patients benefit more if it is added to their current therapies? As usual, more questions are generated by each successful clinical trial. The great news is that we have another treatment option for MS patients and we are learning more about the disease.
For more information on Tysabri, please see Antegren Update Anyone wishing additional information about MS and its treatments may contact MSAA's Helpline consultants by calling (800) 532-7667. Media questions should be directed to Andrea Borkowski at (800) 532-7667, ext. 123.
By Susan Wells Courtney, MSAA Writer
Multiple Sclerosis Association of America
706 Haddonfield Road, Cherry Hill, New Jersey 08002
(800) 532-7667
